Composite seat pan structure for a lightweight aircraft seat assembly

ABSTRACT

An aircraft passenger seat configured in accordance with an embodiment of the invention utilizes composite materials to achieve significant weight savings relative to conventional seat designs. The seat includes one or more lightweight composite support legs, a lightweight composite seat pan, and a lightweight composite seat back structure. The support legs are coupled to the seat pan, which is in turn coupled to the seat back structure. The support legs utilize composite frame elements that are formed as continuous compression molded composite extrusions. The seat pan includes composite fore and aft cross beams that are also formed as continuous compression molded composite extrusions. The aft cross beam includes a rear flange that serves as a flexible “hinge” for the seat back structure. The seat can leverage producible and relatively inexpensive composite manufacturing techniques such that the seat can be economically produced for use as an economy class seat.

TECHNICAL FIELD

Embodiments of the present invention relate generally to aircraftcomponents. More particularly, embodiments of the present inventionrelate to composite structures, components, and assemblies for alightweight aircraft passenger seat.

BACKGROUND

Commercial aircraft utilize different passenger seating configurationsand designs. Historically, aircraft passenger seats have beenmanufactured using heavy and bulky materials that satisfy certainstructural design requirements and passenger comfort requirements. Inthis regard, conventional aircraft passenger seats include a number ofrelatively heavy metal components. Such components can contribute asignificant amount to the overall weight of an aircraft, particularlywhen the aircraft includes seats for hundreds of passengers. Weightreduction is becoming increasingly important in modern aircraft design.A reduction in the weight of the aircraft structure may allow theaircraft to carry more fuel, thus extending the flight range. Areduction in the weight of the aircraft structure may also allow theaircraft to carry additional passengers and/or cargo, thus increasingthe potential profitability of the aircraft.

The amount of legroom and personal space in a commercial aircraftinfluences the overall comfort of the passenger. The size of thepassenger seats and the number of seat rows determines the amount oflegroom and personal space for a given aircraft. In practice, the bulkymaterials and thick padding utilized in conventional aircraft passengerseats consume precious cabin space that could otherwise be used forincreased legroom and/or used for additional rows of seats.Unfortunately, such bulky materials are usually necessary for structuralsupport and thick padding is usually necessary to provide sufficientcushioning for the seated passengers.

Accordingly, it is desirable to have a lightweight passenger seat foraircraft applications. In addition, it is desirable to have a passengerseat for aircraft applications having a smaller fore-aft dimensionrelative to conventional passenger seat designs. Furthermore, otherdesirable features and characteristics of embodiments of the presentinvention will become apparent from the subsequent detailed descriptionand the appended claims, taken in conjunction with the accompanyingdrawings and the foregoing technical field and background.

BRIEF SUMMARY

An aircraft passenger seat configured in accordance with an exampleembodiment of the invention includes a lightweight compositeconstruction that provides weight savings and size reduction compared toconventional seats. The composite construction enables the passengerseat to meet required structural specifications in a compact andlightweight configuration. In one embodiment, the lightweight aircraftpassenger seat utilizes a composite support leg structure having littleor no metal parts. In one embodiment, the lightweight aircraft passengerseat utilizes a composite seat pan assembly having little or no metalparts. In one embodiment, the lightweight aircraft passenger seatutilizes a composite seat back structure. The composite seat panassembly and the composite seat back structure may be coupled togetherusing a composite flange element that serves as a lightweight hingeelement for the seat back structure.

The above and other aspects of an embodiment of the invention may becarried out by a composite seat pan for a lightweight aircraft passengerseat. The composite seat pan includes: a composite fore cross beam; acomposite aft cross beam; and a composite skin having an upper surfaceand an opposite lower surface coupled to the composite fore cross beamand to the composite aft cross beam, the composite skin being configuredas a structural element of the composite seat pan that resists fore-aftbending of the composite fore cross beam and the composite aft crossbeam.

The above and other aspects of an embodiment of the invention may becarried out by a method of manufacturing a composite seat pan for alightweight aircraft passenger seat. The method involves: forming a forecross beam from a first composite extrusion using a continuouscompression molding process; forming an aft cross beam from a secondcomposite extrusion using the continuous compression molding process;structurally joining the fore cross beam to the aft cross beam with aplurality of spreader bars; and structurally coupling a composite skinto the fore cross beam, the aft cross beam, and the spreader bars.

The above and other aspects of an embodiment of the invention may becarried out by a composite seat pan assembly for a lightweight aircraftpassenger seat. The composite seat pan assembly includes: a compositefore cross beam; a composite aft cross beam having a rear flangeconfigured for coupling to a seat back of the lightweight aircraftpassenger seat, the rear flange being flexible and resilient tofacilitate pivoting of the seat back relative to the composite aft crossbeam; and a composite skin having an upper surface and an opposite lowersurface coupled to the composite fore cross beam and to the compositeaft cross beam.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be derived byreferring to the detailed description and claims when considered inconjunction with the following figures, wherein like reference numbersrefer to similar elements throughout the figures.

FIG. 1 is a front perspective view of an embodiment of a lightweightaircraft passenger seat;

FIG. 2 is a front perspective view of a portion of a lightweightaircraft passenger seat;

FIG. 3 is a front perspective view of an embodiment of a composite seatpan for a lightweight aircraft passenger seat;

FIG. 4 is a front perspective view of a portion of a lightweightaircraft passenger seat;

FIG. 5 is a rear perspective view of a portion of a lightweight aircraftpassenger seat;

FIG. 6 is a side view of a portion of a lightweight aircraft passengerseat;

FIG. 7 is a detailed side view of a portion of a lightweight aircraftpassenger seat;

FIG. 8 is a detailed side view of a portion a lightweight aircraftpassenger seat, showing the junction of a composite seat pan and acomposite seat back structure;

FIG. 9 is a perspective cross sectional view of the portion of thelightweight aircraft passenger seat as viewed along line A-A in FIG. 7;

FIG. 10 is a side view of an embodiment of a composite cross beamsuitable for use with a composite seat pan;

FIG. 11 is a cross sectional view of the cross beam shown in FIG. 10, asviewed from line B-B;

FIG. 12 is a cross sectional view of the cross beam shown in FIG. 10, asviewed from line C-C;

FIG. 13 is a side view of an embodiment of a composite skin suitable foruse with a composite seat pan;

FIG. 14 is a perspective view of a seat belt anchor suitable for use inan embodiment of a lightweight aircraft passenger seat;

FIG. 15 is a perspective view of a spreader bar suitable for use in alightweight aircraft passenger seat;

FIG. 16 is a perspective side view of an embodiment of a compositesupport leg of a lightweight aircraft passenger seat;

FIG. 17 is a perspective side view of extruded composite frame elementssuitable for use in the composite support leg shown in FIG. 16;

FIG. 18 is a perspective side view of extruded composite frame elementsand core material suitable for use in the composite support leg shown inFIG. 16;

FIG. 19 is a perspective side view of an embodiment of a compositesupport leg, showing features of a composite side skin;

FIG. 20 is a perspective cross sectional view of the composite supportleg shown in FIG. 16 cut through the core material;

FIG. 21 is a perspective cross sectional view of the composite supportleg shown in FIG. 16 cut through the flanges of the fore frame element;

FIG. 22 is a top view of an embodiment of a composite brace suitable foruse with a composite support leg;

FIG. 23 is a top view of an alternate embodiment of a composite bracesuitable for use with a composite support leg;

FIG. 24 is a side view of another embodiment of a composite support leg,showing floor mounting fittings and a seat back actuator;

FIG. 25 is a perspective view of an embodiment of a fitting suitable foruse with the composite support leg shown in FIG. 24;

FIG. 26 is a perspective view of an embodiment of a composite seat backstructure for a lightweight aircraft passenger seat;

FIG. 27 is a perspective view of an embodiment of a torque box suitablefor use with the composite seat back structure shown in FIG. 26;

FIG. 28 is a perspective cross sectional view of the composite seat backstructure shown in FIG. 26 cut through the major section of the torquebox;

FIG. 29 is a perspective view of an embodiment of an actuator ribsuitable for use with the composite seat back structure shown in FIG.26;

FIG. 30 is a side view of an alternate embodiment of a composite seatback structure for a lightweight aircraft passenger seat; and

FIG. 31 is a perspective cross sectional view of the composite seat backstructure shown in FIG. 30 cut through the major section of the torquebox.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the embodiments of the invention or theapplication and uses of such embodiments. Furthermore, there is nointention to be bound by any expressed or implied theory presented inthe preceding technical field, background, brief summary or thefollowing detailed description.

For the sake of brevity, conventional aspects and techniques related tothe manufacture of composite materials (including the handling andprocessing of particular chemicals, compounds, resins, fibers, andsubstrates) may not be described in detail herein.

The following description may refer to elements or nodes or featuresbeing “connected” or “coupled” together. As used herein, unlessexpressly stated otherwise, “connected” means that oneelement/node/feature is directly joined to (or directly communicateswith) another element/node/feature, and not necessarily mechanically.Likewise, unless expressly stated otherwise, “coupled” means that oneelement/node/feature is directly or indirectly joined to (or directly orindirectly communicates with) another element/node/feature, and notnecessarily mechanically.

FIG. 1 is a front perspective view of a lightweight aircraft passengerseat 100 configured in accordance with an embodiment of the invention.Seat 100 is suitable for use as a passenger seat in an aircraft, e.g.,as a row in a commercial aircraft. Although seat 100 is depicted as atriple seat assembly, the concepts, techniques, features, andtechnologies described herein can be extended to any practical seatconfiguration, such as a double seat, a quad seat, a single seat, or aseat configured to accommodate any number of passengers, limited only bypractical size restrictions, structural material properties, andaircraft configuration. The triple seat configuration depicted in thefigures is not intended to limit or otherwise restrict the use or scopeof the described embodiments in any way. Another embodiment of anaircraft passenger seat having a composite construction is disclosed inU.S. patent application Ser. No. 11/383,867, titled Lightweight AircraftPassenger Seat with Composite Construction (the entire content of whichis incorporated by reference herein).

Seat 100 generally includes a lightweight composite support structure102, a lightweight composite seat pan 104 sized to accommodate threepassengers, three seat cushions 106, three seat back arrangements 108,and three headrests 110. The combination of these main componentsresults in a lightweight and compact (from fore-to-aft) constructionrelative to conventional aircraft seat assemblies. This particularembodiment, it is estimated, weighs about 18 pounds per passenger place(or 54 pounds per triple assembly as embodied herein. This represents asignificant reduction in weight relative to conventional non-compositeseat designs. As a comparison, current best-in-class economy seatstypically weight more than 24 pounds per passenger place.

Lightweight composite support structure 102 has an upper end (hiddenfrom view in FIG. 1) and a lower end that is suitably configured toaccommodate attachment to the floor of the aircraft. The lower end may,for example, be designed for compatibility with seat mounting rails thatare integrated into the floor of the aircraft. The upper end of supportstructure 102 is coupled to the lower side of seat pan 104 usingfasteners, an attachment mechanism, a suitable attachment material orcomposition, or the like. In practice, support structure 102 can betuned according to the seating capacity of the particular aircraft seatassembly (three passengers for seat 100). In this regard, supportstructure 102 (and seat 100 in general) is suitably configured toprovide structural support for three adult passengers and to satisfy anyrequired structural, static, or dynamic tests, such as, for example, the“16G” dynamic testing mandated by the Federal Aviation Administration.

In the illustrated embodiment, lightweight composite support structure102 includes two composite support legs 112. Composite support legs 112may be identical and/or symmetrical to one another, and each compositesupport leg 112 is individually coupled to the lower side of seat pan104 as mentioned above. As described in more detail below, eachcomposite support leg 112 has an upper end that is coupled to the lowerside of seat pan 104 via at least one spreader bar (not shown in FIG.1). An example construction for composite support legs 112 is describedin more detail below with reference to FIGS. 16-25. Seat 100 may alsoinclude a luggage retaining bar 114 coupled to (or located near) supportstructure 102 and/or seat pan 104.

Composite seat pan 104 has an upper side (upon which seat cushions 106are located), a lower side coupled to the upper end of lightweightcomposite support structure 102, a front (fore) section, and a rear(aft) section. In certain embodiments, composite seat pan 104 providesstructural support for passenger armrests and/or provides structuralmounting locations for passenger seat belts. An exemplary constructionfor composite seat pan 104 is described in more detail below withreference to FIGS. 2-5.

Seat cushions 106 are positioned on the upper side of composite seat pan104. Seat 100 may utilize individual and physically distinct seatcushions 106 or a subassembly that includes seat cushions 106 coupledtogether. For example, seat cushions 106 may be joined together via asuitably configured webbing, seam, or connecting material.

Seat back arrangements 108 are coupled to composite seat pan 104 in amanner that enables them to recline and tilt forward as needed. In thisexample embodiment, each seat back arrangement 108 is a separatecomponent, which enables independent pivoting relative to composite seatpan 104. Each seat back arrangement 108 may include a seat backstructure (hidden from view in FIG. 1) and a seat back cushion 116coupled to the seat back structure. The seat back structures providestructural support for the respective seat back cushions 116 and provideback support for the passengers. The seat back structures may be coupledto the rear section of composite seat pan 104 in an appropriate manner.For example, an integrated feature of composite seat pan 104 may serveas an attachment architecture (e.g., a flexible “hinge”) for the seatback structures. Embodiments of a seat back structure suitable for usewith seat 100 are described below with reference to FIGS. 26-31.

An embodiment of a lightweight aircraft passenger seat as describedherein includes several primary structural components: composite supportlegs; a composite seat pan; and composite seat back structures. FIG. 2and FIGS. 4-9 illustrate these main structural components (without anyseat cushions or seat back cushions) and show how they cooperate tofunction as the overall support architecture for the seat. FIG. 2 is afront perspective view of a portion of a lightweight aircraft passengerseat, FIG. 3 is a front perspective view of an embodiment of a compositeseat pan 200, and FIG. 5 is a bottom perspective view of a portion ofthe lightweight aircraft passenger seat—these figures generallyillustrate the manner in which these primary components are coupledtogether. FIG. 5 and FIG. 6 show seat pan 200 coupled to compositesupport legs 300, and coupled to composite seat back structures 400.Each of these main structural components will be described in detailbelow.

Composite Seat Pan

Referring to FIGS. 2-5, composite seat pan 200 generally includes a forecross beam 202, an aft cross beam 204, a skin or membrane 206, and aplurality of spreader bars 208. Seat pan 200 may also include a numberof seat belt anchors 210 coupled to aft cross beam 204. FIG. 4, which isa front perspective view of a portion of an aircraft passenger seat,shows the entire fore cross beam 202 and the entire aft cross beam 204in relation to other structural members of the seat.

Fore cross beam 202 includes a forward flange 212, a rear flange 214,and a generally U-shaped section 216 between forward flange 212 and rearflange 214. Forward flange 212 and rear flange 214 run along the majorlongitudinal axis of fore cross beam 202. U-shaped section 216, whichalso runs along the major longitudinal axis of fore cross beam 202,extends in the downward direction relative to the normal orientation ofthe seat, as depicted in FIG. 7 (which is a detailed side view of aportion of the seat). In this context, the major longitudinal axis offore cross beam 202 (and of aft cross beam 204) runs along the width ofthe seat (see FIG. 4). In other words, the major longitudinal axis offore cross beam 202 corresponds to its longest dimension.

As depicted in FIG. 7, fore cross beam 202 has an asymmetriclongitudinal cross section that is suitably configured to provide adirectional load-bearing characteristic. In this regard, U-shapedsection 216 is designed to provide structural support to primarilyaccommodate loading in the up-down direction rather than in the fore-aftdirection. U-shaped section 216 is relatively stiff and resistant tovertical deflection, and is less stiff and less resistant to horizontalbending (where “vertical” and “horizontal” are relative to the usualseating orientation shown in the figures). This asymmetric configurationallows fore cross beam 202 to be manufactured with less material (toreduce weight) because fore cross beam 202 need not withstand highloading in the fore-aft direction. As described in more detail below,skin 206 is suitably configured as a structural element that cooperateswith fore cross beam 202 and aft cross beam 204 to withstand suchfore-aft loading. In contrast to the asymmetric cross section of forecross beam 202, a traditional cross beam formed from round tube stock(e.g., a round metal tube) has a symmetric longitudinal cross sectionthat provides a symmetric load-bearing characteristic.

In certain embodiments, fore cross beam 202 has a non-uniform crosssection, relative to its major longitudinal axis. In other words, thecross sectional configuration of fore cross beam 202 changes along itslength. In this regard, FIG. 10 is a simplified side view of fore crossbeam 202 (FIG. 10 may also represent a side view of aft cross beam 204),FIG. 11 is a cross sectional view as viewed from line B-B in FIG. 10,and FIG. 12 is a cross sectional view as viewed from line C-C in FIG.10. The non-uniform cross section reinforces fore cross beam 202 at oneor more mounting locations for the support legs 218 of the seat. Forexample, fore cross beam 202 may be suitably configured to provideadditional stiffness and strength at and between support legs 218. Inthe illustrated embodiment, U-shaped section 216 of fore cross beam 202has a non-uniform thickness near its lowermost segment: U-shaped section216 is thicker in the span of fore cross beam 202 at and between supportlegs 218 and is thinner outside this span. This non-uniform thickness isshown in dashed lines in FIG. 10. FIG. 11 depicts the relatively thincross section of fore cross beam 202 and FIG. 12 depicts the relativelythick cross section of fore cross beam 202. In the illustratedembodiment, the thinner U-shaped section 216 is about 0.1 to 0.2 inchthick, while the thicker U-shaped section 216 is about 0.3 to 0.7 inchthick. The gauge of fore cross beam 202 elsewhere remains substantiallyconstant over its longitudinal aspect—approximately 0.05 inch to 0.07inch thick in certain embodiments. The non-uniform nature of fore crossbeam 202 results in weight savings due to precise optimization ofstrength characteristics accomplished by tailoring the beam thicknessesto the loads imparted locally along the beam.

Fore cross beam 202 may be formed from a lightweight metal such asaluminum or titanium, a high strength molded plastic, or any suitablematerial or combination of materials. In one embodiment, fore cross beam202 is formed as a one-piece composite construction. For example, forecross beam 202 can be realized as an extruded composite beam. Inparticular, fore cross beam 202 may be a continuous compression moldedcomposite beam that is formed using an appropriate continuouscompression molding process. This process results in a producible forecross beam 202 that might otherwise be too costly to manufacture.Briefly, one such process begins with composite sheets of laminatedthermoplastic and fiber material (each sheet may have any number oflayers, and each sheet may be about 0.005 inch thick). The processemploys heat and pressure to fuse multiple sheets together and to formthe sheets into the desired shape. For example, fore cross beam 202 maybe manufactured from 10-15 individual sheets of material. The thickerarea of U-shaped section 216 may be formed by molding extra layers whereneeded.

One embodiment of fore cross beam 202 includes a thermoplastic resin andat least one layer of carbon graphite fiber material that has beentreated using the continuous compression molding process describedabove. In a practical deployment, the thermoplastic resin ispolyetherketoneketone (PEKK), which satisfies certain flammability,smoke emission, and toxicity requirements (for example, PEKK melts at avery high temperature of approximately 700° F.). Polyetherimide (PEI) isanother thermoplastic resin that is suitable for use in the variousapplications described herein. Of course, other composite materials,resins, and fibers may be used in an embodiment of fore cross beam 202.

In practice, fore cross beam 202 is formed as a composite extrusion frommaterial having directional fibers, where the extrusion includes aspecific layup configuration that is optimized to reduce weight whileretaining the desired structural characteristics. Generally, this layupis such that at least thirty percent of the fibers in the compositeextrusion are oriented within the range of ±30 degrees relative to themajor longitudinal axis of fore cross beam 202. For reference, thelongitudinal axis corresponds to the zero degree reference direction. Inone embodiment, more than fifty percent of the fibers in the compositeextrusion are oriented at approximately ±5 degrees relative to the majorlongitudinal axis of fore cross beam 202, and less than fifty percent ofthe fibers in the composite extrusion are oriented at approximately ±65degrees relative to the major longitudinal axis of fore cross beam 202.In one specific embodiment, approximately eighty percent of the fibersin the composite extrusion are oriented at approximately ±5 degreesrelative to the major longitudinal axis of fore cross beam 202, andapproximately twenty percent of the fibers in the composite extrusionare oriented at approximately ±65 degrees relative to the majorlongitudinal axis of fore cross beam 202. This specific layup mayinclude, for example, eight plies having fibers oriented atapproximately ±5 degrees, and two plies having fibers oriented atapproximately ±65 degrees, alternating in a suitable layering scheme.The thicker portion of U-shaped section 216 may include any number ofadditional plies (oriented at ±5 degrees and/or ±65 degrees) that arecompression molded into the extrusion as described above.

Aft cross beam 204 is generally configured as described above for forecross beam 202 (features, aspects, and elements of aft cross beam 204that are shared with fore cross beam 202 will not be redundantlydescribed in detail here). In practice, aft cross beam 204 may have adifferent shape than fore cross beam 202 to accommodate the desiredcontour of skin 206 and/or to provide different structuralcharacteristics. Aft cross beam 204 includes a forward flange 220, arear flange 222, and a generally U-shaped section 224 between forwardflange 220 and rear flange 222. As with fore cross beam 202, aft crossbeam 204 may have a non-uniform cross section, relative to its majorlongitudinal axis, that provides additional rigidity and strength nearthe support legs of the aircraft passenger seat. For this embodiment,aft cross beam 204 is also formed as a continuous compression moldedcomposite beam, which preferably has the composition and layup describedabove for fore cross beam 202.

Referring to FIGS. 6-8, an embodiment of aft cross beam 204 includesrear flange 222, which is configured for coupling to a seat back of thepassenger seat. FIG. 6 is a side view of a portion of the aircraftpassenger seat, showing the entire seat pan 200 and seat back structure400, and FIG. 8 is a detailed side view of a portion of the passengerseat, showing the junction of seat pan 200 and seat back structure 400.In this example, rear flange 222 may be coupled to seat back structure400 using fasteners, adhesive, welding, or some combination of theabove. In practice, rear flange 222 is flexible and resilient tofacilitate pivoting of seat back structure 400 relative to compositeseat pan 200, thus forming a hinge which enables the seat back torecline for passenger comfort. Referring to FIG. 8, rear flange 222 hasan upper surface that is coupled to the lower surface of skin 206, andrear flange 222 has a lower surface that is configured for coupling toan upper surface 226 of seat back structure 400. In this regard, aftcross beam 204 and seat back structure 400 may be coupled together toform an assembly of the aircraft passenger seat, where rear flange 222serves as a hinge between skin 206 and seat back structure 400.

Skin 206 has an upper surface 228 and an opposite lower surface 230.Upper surface 228 represents the support surface of seat pan 200. Asbest depicted in FIG. 5, lower surface 230 is coupled to composite forecross beam 202, to composite aft cross beam 204, and to spreader bars208. In an embodiment of seat pan 200, skin 206 is configured as astructural element that resists fore-aft bending of fore cross beam 202and aft cross beam 204. In other words, skin 206 functions to increasethe strength of seat pan 200 for purposes of the fore-aft load path. Asmentioned above, the structural characteristic of skin 206 allows forecross beam 202 and aft cross beam 204 to be lightened because the crossbeams and spreader bars need not provide all the fore-aft strength andrigidity for seat pan 200. As a simple analogy, skin 206, fore crossbeam 202, and aft cross beam 204 are akin to a structural I-beamrelative to the fore-aft direction.

Referring to FIG. 2 and FIG. 3, skin 206 may include reinforcing strips(or any suitably shaped elements) that provide enhanced rigidity andstrength in attachment areas of skin 206. These attachment areas maycorrespond to cross-beam-to-skin junctions and/or tospreader-bar-to-skin junctions for seat pan 200. In this regard, skin206 may include fore-aft reinforcing strips 232 and longitudinalreinforcing strips 234 coupled thereto or formed therein. In thisembodiment, fore-aft reinforcing strips 232 are located over the uppermounting surfaces of spreader bars 208, and longitudinal reinforcingstrips 234 are located over the flanges of fore cross beam 202 and aftcross beam 204. Reinforcing strips 232/234 are suitably configured toincrease the strength, toughness, and shear resistance of skin 206 inthe designated attachment areas, which may be penetrated by rivets,screws, bolts, or other fasteners during assembly of seat pan 200.

In certain embodiments, each longitudinal reinforcing strip 234 has anon-uniform cross section, relative to its major longitudinal axis. Inother words, the cross sectional configuration of each longitudinalreinforcing strip 234 changes along its length (similar to thatdescribed above in connection with the non-uniform cross section of forecross beam 202). In this regard, FIG. 13 is a simplified side view ofskin 206 in exaggerated scale. FIG. 10 may also represent a crosssectional view of a longitudinal reinforcing strip 234 cut through itsmajor longitudinal axis. The non-uniform cross section of thelongitudinal reinforcing strip 234 reinforces skin 206 at one or moremounting locations for the support legs 218 of the seat. For example,longitudinal reinforcing strip 234 may be suitably configured to provideadditional stiffness and strength at and between support legs 218. Inthe illustrated embodiment, longitudinal reinforcing strip 234 isthicker at and between support legs 218 and is thinner outside thisspan. This non-uniform thickness is shown in an exaggerated manner inFIG. 13. The non-uniform nature of skin 206 results in weight savingsdue to precise optimization of strength characteristics accomplished bytailoring the pan thicknesses to the loads imparted locally along thepan.

Skin 206 may be formed as a composite, or formed from a lightweightmetal such as aluminum or titanium, a high strength molded plastic, orany suitable material or combination of materials. In one embodiment,skin 206 is formed as a one-piece composite construction. For example,composite skin 206 can be primarily formed from a thermoplastic resinand at least one layer of aramid fiber material (e.g., KEVLAR material).For the reasons mentioned above, PEKK is one thermoplastic resin that isparticularly suitable for composite skin 206, and PEI is anothersuitable thermoplastic resin. This particular composite construction isdesirable to provide toughness for composite skin 206 (rather thanstiffness and rigidity). Thus, composite skin 206 exhibits resiliencyand rip-stop characteristics that allow it to withstand some puncturingwithout breaking. Of course, alternative composite constructions may beutilized for composite skin 206, possibly at the cost of additionalweight. On the other hand, reinforcing areas of composite skin, such asfore-aft reinforcing strips 232 and longitudinal reinforcing strips 234,may be formed with at least one layer of carbon graphite fiber material.The carbon graphite fiber material adds stiffness and rigidity tocomposite skin 206 in these reinforcement areas. Of course, othercomposite materials, resins, and fibers may be used in an embodiment ofcomposite skin 206.

In one embodiment, composite skin 206 is formed as a unitary contouredpiece having a nominal thickness of about 0.010 inch to about 0.040inch. This nominal thickness represents areas having no reinforcingstrips 232/234. Fore-aft reinforcing strips 232, however, may be formedby adding one or more layers of carbon graphite fiber material, aramidfiber material, or any suitable reinforcing material (approximately oneinch wide) in the attachment areas, resulting in an overall thickness ofabout 0.070 inch in the respective reinforcing areas. Likewise,longitudinal reinforcing strips 234 may be formed from one or moreadditional layers of carbon graphite fiber material, aramid fibermaterial, or any suitable reinforcing material (approximately one inchwide). As described above with reference to FIG. 13, a relatively highnumber of additional layers of fiber material may be used to form thethicker portion of longitudinal reinforcing strips 234, while arelatively low number of additional layers of fiber material may be usedto form the thinner portion of longitudinal reinforcing strips 234. Inone practical embodiment, composite skin 206 is formed by sandwichingthe carbon graphite fiber reinforcing material between two layers ofKEVLAR composite.

In an alternate embodiment, seat pan 200 utilizes a composite sandwichconstruction in lieu of a unitary skin 206. In this alternateembodiment, seat pan 200 utilizes two skins (which may be configuredsubstantially as described herein for skin 206) with a suitable corematerial, such as honeycomb, located between the two skins.

FIG. 14 is a perspective view of a seat belt anchor 210 suitable for usein an embodiment of a lightweight aircraft passenger seat. FIGS. 7-9depict seat belt anchors 210 installed in composite aft cross beam 204.Seat belt anchors 210 may be formed from a composite material, a highstrength molded plastic, a lightweight metal such as aluminum ortitanium, or any suitable material or combination of materials.Referring to FIG. 14, seat belt anchor 210 generally includes a forwardflange 236, a rear flange 238, and a web 240 between flanges 236/238.Seat belt anchor 210 may also have a protrusion 242 and a mounting hole244 formed in protrusion 242. In this embodiment, protrusion 242 isformed as an extension of web 240. For this example, flanges 236/238 andweb 240 are each approximately 0.08 inch thick.

As best illustrated in FIG. 8, seat belt anchor 210 is coupled withinU-shaped section 224 of aft cross beam 204 such that forward flange 236is flush against the forward “leg” of U-shaped section 224, and suchthat rear flange 238 is flush against the rear “leg” of U-shaped section224. For this embodiment, rear flange 238 is angled relative to forwardflange 236 (which is nominally oriented in a vertical position). Inpractice, seat belt anchors 210 are coupled to aft cross beam 204 byfastening forward flanges 236, U-shaped section 224, and spreader bars208 together along the forward span of aft cross beam 204, and byfastening rear flanges 238 to U-shaped section 224 along the rear spanof aft cross beam 204. FIG. 4 shows only a few seat belt anchors 210installed in aft cross beam 204, and FIG. 3 shows all of the seat beltanchors 210 (only the protrusions 242 of seat belt anchors 210 arevisible after composite skin 206 is in place).

Protrusions 242 and mounting holes 244 accommodate passenger seat belts(not shown) for the aircraft seat. For example, the seat belts can beattached to protrusions 242 using suitable fasteners inserted intomounting holes 244. Referring to FIG. 2, protrusions 242 and mountingholes 244 may also accommodate passenger armrest assemblies 246 for theaircraft seat. For example, a mounting feature of armrest assemblies 246can be positioned between two protrusions 242 and secured using suitablefasteners inserted into mounting holes 244. For the illustratedembodiment, four armrest assemblies 246 are used for three passengers.

Referring to FIG. 3, one embodiment of composite seat pan 200 may employeight identical seat belt anchors 210. An alternate embodiment ofcomposite seat pan 200 may employ two end seat belt anchors (notseparately shown) for the two ends of seat pan 200, and four identicalseat belt anchors 210 for the middle of seat pan 200. Each of the twoend seat belt anchors may resemble two of the single seat belt anchors210 integrated into a one-piece component. Referring to FIG. 4, the useof different seat belt anchors at the ends of seat pan 200 may bedesirable to accommodate the particular arrangement and location ofspreader bars 208. The relationship between seat belt anchor positionand spreader bar position is described in more detail below.

FIG. 15 is a perspective view of a spreader bar 208 suitable for use incomposite seat pan 200. FIG. 4 and FIG. 5 depict spreader bars 208coupled to composite fore cross beam 202 and to composite aft cross beam204. Spreader bars 208 may be formed from a lightweight metal such asaluminum, a composite material, a high strength molded plastic, or anysuitable material or combination of materials. In this embodiment,spreader bars 208 are formed from aluminum. Referring to FIG. 15,spreader bar 208 generally includes a fore flange 248, an aft flange250, an upper flange 252, and a rib 254 between flanges 248/250. Forthis example, rib 254 is about 0.08 inch thick, and upper flange 252varies from about 0.15 inch thick to about 0.25 inch thick. Spreader bar208 may include a plurality of mounting holes 256 formed within rib 254(mounting holes 256 are utilized to attach spreader bars 208 to thecomposite support legs as described below). Spreader bar 208 may alsoinclude mounting holes 258 formed within flanges 248/250, where mountingholes 258 are used to attach spreader bars 208 to composite cross beams202/204 of seat pan 200.

As best illustrated in FIGS. 4, 5, and 7, spreader bars 208 function asstructural support members for composite seat pan 200; spreader bars208, fore cross beam 202, and aft cross beam 204 effectively form asupport “frame” for composite skin 206. Referring to FIG. 7, fore flange248 of spreader bar 208 is coupled to fore cross beam 202 (at itsU-shaped section 216), aft flange 250 of spreader bar 208 is coupled toaft cross beam 204 (at its U-shaped section 224), and upper flange 252of spreader bar 208 is coupled to the lower surface 230 of compositeskin 206. In practice, fore flange 248 is configured for flush mountingwith the rear “leg” of the U-shaped section 216 of fore cross beam 202,and aft flange 250 is configured for flush mounting with the forward“leg” of the U-shaped section 224 of aft cross beam 204. For thisembodiment, flanges 248/250 of spreader bars 208 are nominally orientedin a vertical position. In practice, spreader bars 208 are coupled tofore cross beam 202, to aft cross beam 204, and to composite skin 206using suitable fasteners and/or bonding techniques.

Referring to FIG. 4, one embodiment of composite seat pan 200 may employeight spreader bars 208 in four mirror-image pairs. In such anembodiment, a mirror-image pair of spreader bars 208 may be coupledtogether (or located in close proximity to each other) for use as endspreader bars for the two ends of seat pan 200. Another embodiment ofseat pan 200 utilizes two “double” spreader bars (not separately shown)for the ends of seat pan 200 and two mirror-image pairs of spreader bars208 for the middle of seat pan 200. The mirror-image pairs also functionas mounting brackets for the composite support legs, as described inmore detail below. Referring to FIG. 4, the use of different spreaderbars at the ends of seat pan 200 may be desirable to accommodate thelack of support legs at the ends of seat pan 200.

Spreader bars 208 are suitably configured to provide a variety ofstructural characteristics for composite seat pan 200. In this regard,spreader bars 208 hold fore cross beam 202 and aft cross beam 204 in aspaced-apart relationship, stabilize cross beams 202/204, and preventmovement and rotation of cross beams 202/204. Moreover, spreader bars208 couple seat pan 200 to the composite support legs, thus establishinga load path from seat pan 200 to the support legs. In one embodiment,spreader bars 208 prevent buckling of composite skin 206, and compositeskin 206 functions as a structural web between cross beams 202/204 andwrinkling may compromise its structural performance. Alternatively,composite skin 206 may be designed to buckle (within certain limits) tofunction as an intermediate diagonal tension web (i.e., a post-buckledweb). Such a configuration enables seat pan 200 to carry loads underpost-buckle conditions.

Spreader bars 208 are configured and arranged to provide an efficientand simple load path from seat belt anchors 210 to cross beams 202/204and to composite skin 206. In this regard, FIG. 9 is a perspective crosssectional view of the portion of the lightweight aircraft passenger seatas viewed along line A-A in FIG. 7. Notably, spreader bars 208 aregenerally shaped as I-beams for purposes of fore-aft load transfer. Inthe illustrated embodiment, the webs 240 of seat belt anchors 210 arealigned (or approximately aligned) with the ribs 254 of spreader bars208. This alignment is desirable to establish a direct (as close aspractical) load path from seat belt anchors 210 to spreader bars 208and, in turn, to the support legs. This simple and efficient load pathenables the aircraft passenger seat to satisfy structural and impactspecifications using a lightweight and compact construction.

An embodiment of a lightweight aircraft passenger seat can bemanufactured with composite seat pan 200. In this regard, seat pan 200can be manufactured as a subassembly that includes: fore cross beam 202;aft cross beam 204; composite skin 206; spreader bars 208; seat beltanchors 210; and fasteners. The manufacturing procedure may include theforming of fore cross beam 202 from a first composite extrusion using acontinuous compression molding process as described above, and theforming of aft cross beam 204 from a second composite extrusion usingthe continuous compression molding process. As mentioned above, eachcross beam 202/204 is preferably formed from multiple plies, where eachply comprises a thermoplastic resin (such as PEKK) and at least onelayer of carbon graphite fiber material. For this embodiment, each crossbeam 202/204 is formed from the preferred layup described above, andeach cross beam 202/204 exhibits a non-uniform cross section along itsmajor longitudinal axis for purposes of reinforcement in the desiredlocations.

The manufacturing process also includes the forming of composite skin206. As mentioned above, composite skin 206 can be manufactured fromthermoplastic resin (such as PEKK), at least one layer of aramid fibermaterial (such as KEVLAR material), and carbon graphite fiber materialthat serves as reinforcing material. Alternatively, composite skin 206may be initially formed with a uniform thickness that is subsequentlyground or machined to form thinner areas, while preserving thicker“reinforced” areas.

In accordance with one suitable manufacturing process, mounting holesfor seat belt anchors 210 and spreader bars 208 are drilled into aftcross beam 204 and seat belt anchors 210 are inserted into aft crossbeam 204. Next, spreader bars 208, aft cross beam 204, and seat beltanchors 210 are fastened together using rivets, bolts, or any suitablefastener (see FIG. 8 and FIG. 9). For the sake of clarity andsimplicity, fasteners are not shown in the figures. Similarly, mountingholes for spreader bars 208 are drilled into fore cross beam 202 and,thereafter, spreader bars 208 and fore cross beam 202 are fastenedtogether, resulting in a support frame for composite skin 206. In thismanner, fore cross beam 202 is structurally joined to aft cross beam 204with spreader bars 208.

Slots for the protrusions 242 of seat belt anchors 210 are formed withincomposite skin 206 before composite skin 206 is installed onto thesupport frame. The slots allow protrusions 242 to extend above compositeskin 206 after seat pan 200 is assembled. Thus, once the slots have beenformed, composite skin 206 can be structurally coupled to fore crossbeam 202, aft cross beam 204, and spreader bars 208. In one embodiment,the lower surface 230 of composite skin 206 is bonded to the exposedupper surfaces of: forward flange 212 of fore cross beam 202; rearflange 214 of fore cross beam 202; forward flange 220 of aft cross beam204; rear flange 222 of aft cross beam 204; and upper flanges 252 ofspreader bars 208. Thereafter, the bonded joint locations can be drilledand secured together using rivets, bolts, or any suitable fasteners. Forexample, fastener holes may be drilled about every two inches along thelength of cross beams 202/204 and along the length of spreader bars 208.As an alternative to adhesive bonding, thermoplastic welding utilizingresistive implants, lasers, or friction stirring are possible. Theresulting seat pan 200 can then be readied for attachment of thecomposite support legs (described below).

Composite Support Legs

In preferred embodiments, each composite support leg 300 employs acomposite construction that is lightweight and producible in acost-efficient manner. For example, each composite support leg 300 canbe manufactured with a resulting weight of less than 1.5 pounds.Referring to FIGS. 16-25, each composite support leg 300 generallyincludes a structural box 302, a brace 304, a front fitting 306, and arear fitting 308. FIG. 16 is a perspective side view of an embodiment ofsupport leg 300 (where rear fitting 308 remains unassembled). FIG. 16also shows spreader bars 208 to demonstrate how support leg 300 iscoupled to seat pan 200.

Structural box 302 represents the main structural component of compositesupport leg 300. This embodiment of structural box 302 is generallytriangular in shape, having an upper seat end 310 and a lower foot end312 opposite seat end 310. Seat end 310 represents the end that will becoupled to seat pan 200, while foot end 312 represents the end that willbe coupled to the floor of the aircraft. For this example, structuralbox 302 includes: a generally triangular outer frame 314; a first skin316 coupled to one side of outer frame 314; a second skin 318 coupled tothe other side of outer frame 314; and core material 320 coupled to andsurrounded by outer frame 314. Core material 320 is also located betweenskins 316/318 and, in certain embodiments, core material 320 is coupledto skins 316/318.

Outer frame 314 may include a plurality of extruded composite frameelements (three in this embodiment) that combine to form the generallytriangular shape. In practice, the three composite frame elements neednot be coupled together to form an integral outer frame 314 (as depictedin FIG. 16). Rather, the individual frame elements can be coupledtogether when structural box 302 is assembled. In alternate embodiments,outer frame 314 may employ frame elements formed from a lightweightmetal such as aluminum or titanium, a high strength molded plastic, anon-extruded composite, or any suitable material or combination ofmaterials.

In one embodiment of composite support leg 300, each of the frameelements is a continuous compression molded composite element that isformed using an appropriate continuous compression molding process, asdescribed above in the context of composite seat pan 200 (alternatively,outer frame 314 can be manufactured using traditional composite layeringtechniques). Indeed, the frame elements may be cut from a singleextrusion that includes a thermoplastic resin (e.g., PEKK) and at leastone layer of carbon graphite fiber material that has been formed usingthe continuous compression molding process. Of course, other compositematerials, resins, and fibers may be used in an embodiment of outerframe 314. An embodiment of outer frame 314 may utilize extrudedcomposite frame elements having the layup configuration described abovein the context of fore cross beam 202. In one specific embodiment,approximately eighty percent of the fibers in the composite extrusionare oriented at approximately ±5 degrees relative to the majorlongitudinal axis of the extrusion, and approximately twenty percent ofthe fibers in the composite extrusion are oriented at approximately ±65degrees relative to the major longitudinal axis of the extrusion.

In the illustrated embodiment, outer frame 314 is formed from acomposite extrusion having a generally C-shaped cross section.Alternatively, outer frame 314 may be formed from a composite extrusionhaving any suitable and producible cross sectional shape, including,without limitation: L-shaped; U-shaped; Z-shaped; I-shaped; T-shaped;W-shaped; π-shaped; V-shaped; Ω-shaped; or a closed shape such as asquare or rectangular tube. The C-shaped cross section and the extrudedcomposite construction of outer frame 314 results in a very strong,rigid, and stiff perimeter for structural box 302; the extruded frameelements serve as the primary stress members for composite support leg300. For this example, the thickness of the frame elements (i.e., theheight of the C) is about 1.25 inches, and the height of the frameelement flanges is about 0.75 inches. Moreover, the extruded frameelements are approximately 0.10 inch thick (which represents about 20molded plies).

Referring to FIG. 18 and FIG. 20, core material 320 is located inside ofouter frame 314, and core material 320 functions to stabilize outerframe 314 (and to stabilize composite skins 316/318 of structural box302). Core material 320 is a lightweight filler material or compositionthat provides additional structural integrity to outer frame 314. Inthis example, core material 320 is formed from a suitable honeycombmaterial, such as HEXWEB honeycomb material (available from HexcelCorporation), NOMEX material (available from DuPont), or the like.Alternatively, core material 320 may include or be formed from a metalhoneycomb, plastic foam, graphite foam, or the like. In the exampleembodiment, the honeycomb core material 320 may have cells that aregenerally orthogonal relative to composite skins 316/318. The honeycombcore material 320 is preferably sandwiched between, and coupled to,composite skins 316/318. The honeycomb core material 320 may also becoupled to the inside surface of outer frame 314. In practice, thehoneycomb core material 320 may be attached to composite skins 316/318and to outer frame 314 using a suitable glue, adhesive, epoxy, or thelike. Additionally or alternatively, this sandwich construction may becoupled together using fasteners or any suitable attachment mechanism orarchitecture.

Skins 316/318 are of similar construction and, in the illustratedembodiment, are “mirror images” of each other. First skin 316 is coupledto the extruded composite frame elements on one side of outer frame 314,and second skin 318 is coupled to the extruded composite frame elementson the opposite side of outer frame 314. When structural box 302 isassembled, first skin 316 corresponds to the first major side ofstructural box 302, and second skin 318 corresponds to the second majorside of structural box 302. Skins 316/318 function to hold the elementsof structural box 302 together, while core material 320 serves tostabilize and prevent buckling of skins 316/318. In addition, skins316/318 function as structural elements that transfer loads from brace304 and propagate the loads to spreader bars 208 and to skin 206 of seatpan 200.

Skins 316/318 may be formed from a composite material, a lightweightmetal such as aluminum or titanium, a high strength molded plastic, orany suitable material or combination of materials. In one embodiment ofcomposite support leg 300, each of the skins 316/318 is a compositeconstruction that is formed from a thermoplastic resin (e.g., PEKK) andat least one layer of carbon graphite fiber material. Of course, othercomposite materials, resins, and fibers may be used in embodiments ofcomposite skins 316/318. For the illustrated example, each compositeskin 316/318 may have a nominal thickness of about 0.030 inch. Referringto FIG. 19, each composite skin 316/318 may also include reinforcingpad-up areas corresponding to mounting locations for components ofcomposite support leg 300. For example, composite skin 316 includes areinforcing pad-up area 322 corresponding to composite brace 304, and areinforcing pad-up area 324 corresponding to front fitting 306. FIG. 21illustrates how these reinforcing pad-up areas provide additionalstructural support for composite brace 304 and front fitting 306. Thesereinforcing pad-up areas can be formed during manufacturing of compositeskins 316/318 by adding additional material (e.g., one or more pieces orlayers of carbon graphite fiber material) where desired. In oneembodiment, composite skins 316/318 are approximately 0.1 inch thick inthese reinforcing pad-up areas.

An alternate embodiment of composite support leg 300 employs outer frame314 without any core material 320 (and possibly without skins 316/318).Such an embodiment may utilize a stronger configuration for outer frame314, for example, thicker composite extrusions, which enables outerframe 314 to serve as a structural truss.

Brace 304 may be formed from a composite construction, a lightweightmetal such as aluminum or titanium, a high strength molded plastic, orany suitable material or combination of materials. In preferredembodiments, brace 304 is of a composite construction. Composite brace304 is best depicted in FIG. 16 and FIG. 22 (which is a top view ofcomposite brace 304). Composite brace 304 has a first end 326 that iscoupled to structural box 302, and a second end 328 that extends awayfrom seat end 310 of structural box 302; second end 328 also extendsaway from foot end 312 of structural box. Second end 328 is suitablyconfigured for attachment to an aircraft mounting feature. In thisembodiment, second end 328 is coupled to rear fitting 308.

FIG. 16 shows mounting holes for an embodiment of composite brace 304and FIG. 22 depicts the mounting holes in dashed lines. The two outermounting hole locations allow first end 326 of composite brace 304 to becoupled to outer frame 314 and composite skins 316/318 of structural box302. The three inner mounting hole locations allow first end 326 ofcomposite brace 304 to be coupled to composite skins 316/318 and to corematerial 320. In this regard, composite brace 304 may include a firstflange 330 and an opposing second flange 332 (see FIG. 22). Thus, whencomposite support leg 300 is assembled, first flange 330 is coupled toone side of structural box 302 and second flange 332 is coupled to theother side of structural box 302.

In this embodiment, composite brace 304 resembles a C-channel with aportion removed to accommodate structural box 302. FIG. 22 shows anopening 334 in composite brace 304 that receives structural box 302 (seeFIG. 16). Alternatively, composite support leg 300 may utilize acomposite brace 336 having an Ω-shaped cross section (see FIG. 23 andFIG. 24). Composite brace 336 is similar to composite brace 304,however, composite brace 336 includes stiffening flanges 338 thatcorrespond to the horizontal segments of the Ω shape. Stiffening flanges338 provide additional structural support to composite brace 336,especially at flanges 340/342.

In practice, composite braces 304/336 can be realized as extrudedcomposite elements formed from a thermoplastic resin (e.g., PEKK) and atleast one layer of carbon graphite fiber material, as described above inthe context of composite cross beams 202/204 for seat pan 200. Indeed,the same continuous compression molding process described above can beutilized to manufacture the composite extrusions used for compositebraces 304/336.

In operation, composite braces 304/336 serve as tension link members forcomposite support leg 300. Referring to FIG. 7 and FIG. 24, rear fitting308 may be used to couple composite braces 304/336 to the floor of theaircraft. Rear fitting 308 may, for example, be formed from alightweight metal such as titanium or aluminum. When coupled to thefloor of the aircraft, composite braces 304/336 function to preventforward movement of the seat. In one embodiment, composite braces304/336 are suitably configured to withstand at least 6500 pounds ofweight in tension.

Front fitting 306 is coupled to foot end 312 of structural box 302, asdepicted in FIGS. 16-19. Here, front fitting 306 is coupled to outerframe 314 proximate foot end 312 using rivets, bolts, or any suitablefasteners. This embodiment of front fitting 306 is configured for rigidattachment to an aircraft mounting feature, such as seat tracks, seatrails, or the like. Front fitting 306 may, for example, be formed from alightweight metal such as aluminum or titanium.

FIG. 24 and FIG. 25 illustrate a shock-absorbing front fitting 344 thatmay be employed in lieu of rigid front fitting 306 (a similarshock-absorbing fitting may also be used in lieu of a rigid rear fitting308). Front fitting 344 may be formed from a lightweight metal such astitanium or aluminum, a high strength molded plastic, a compositeconstruction, or any suitable material or combination of materials. Forthis embodiment, front fitting 344 is formed from a metal. As shown inFIG. 24, shock-absorbing front fitting 344 is coupled to foot end 312 ofstructural box 302 (more specifically, front fitting 344 is coupled toouter frame 314). The base of front fitting 344 is configured forattachment to an aircraft mounting feature, e.g., seat tracks or a seatrail. Front fitting 344 is suitably configured to absorb energy and tofacilitate limited travel of structural box 302 toward the aircraftmounting feature under high loading conditions. The arrow 346 in FIG. 24represents this limited amount of travel. For this example, frontfitting 344 is designed to allow about 1.2 inches of travel under highloading conditions. This shock-absorbing characteristic emulates flexingor bending of traditional metal-based aircraft passenger seats.

Referring to FIG. 25, an embodiment of shock-absorbing front fitting 344may include a generally C-shaped channel section 348 having two opposingmounting flanges 350. Mounting flanges 350 are configured to allowcoupling of front fitting 344 to structural box 302 (see FIG. 24). Frontfitting 344 may also have a foot 352 that is suitably configured toallow coupling of front fitting 344 to a feature on the aircraft floor.Notably, mounting flanges 350 are angled relative to the floor mountingsurface because this angle roughly corresponds to the direction oftypical load paths contemplated by front fitting 344. This embodiment offront fitting 344 includes three slots 354 formed within, but onlypartially through, each mounting flange 350. Slots 354 may be formed bymilling some of the material away from mounting flanges 350. The lengthof slots 354 determines the amount of allowable travel of structural box302, and the width of slots 354 is dictated by the size of the mountinghardware.

Each slot 354 has a fastener hole 356 formed therein, where eachfastener hole 356 is configured to receive a fastener for couplingshock-absorbing front fitting 344 to foot end 312 of structural box 302.For this example, fastener holes 356 are formed at or near the top ofslots 354, as shown in FIG. 25. FIG. 24 shows the normal installationand operating configuration of composite support leg 300 with frontfitting 344 coupled to structural box 302. Under normal operatingconditions, structural box 302 is maintained in the position shown inFIG. 24 because fastener holes 356 and mounting flanges 350 remainintact to prevent travel of structural box 302 relative to foot 352 offront fitting 344. However, high loading conditions on seat end 310 ofstructural box 302 cause the fasteners in fastener holes 356 to shearthrough mounting flanges 350 in the area defined by slots 354. In otherwords, the intentionally weakened web within slots 354 deforms to allowstructural box 302 to move in a downward direction toward foot 352. Thisdeformation absorbs an appreciable amount of energy and shock that wouldotherwise need to be absorbed elsewhere by other means. Notably, thematerial used for front fitting 344, the shape and size of slots 354,the gauge of mounting flanges 350, and/or the amount of material removedto create slots 354 can be tuned to achieve the desired load bearing anddeflection characteristics for front fitting 344.

Referring to FIGS. 16, 20, and 21, structural box 302 can be coupled tospreader bars 208 during assembly of the lightweight aircraft passengerseat. As best shown in FIG. 20, the flanges of outer frame 314 cooperatewith ribs 254 of spreader bars 208, which are preferably aligned withwebs 240 of seat belt anchors 210 (as described above in connection withseat pan 200). As mentioned above, this configuration establishes anefficient, simple, and effective load path from seat belt anchors 210 toseat pan 200 and to support legs 300.

An embodiment of a lightweight aircraft passenger seat can bemanufactured with composite support legs 300. In this regard, eachsupport leg 300 can be manufactured as a subassembly in the followingmanner. The manufacturing procedure may include the forming of acomposite extrusion having a suitable composition, using a continuouscompression molding process as described above. Then, extruded compositeframe elements can be obtained from the composite extrusion (these frameelements will be used to create outer frame 314). In addition, the twocomposite skins are formed in the configurations described above usingthermoplastic resin and carbon graphite fiber material.

The structural box 302 can be produced in the following manner.Indexing/alignment holes in the composite frame elements enable thecomposite frame elements to be held in a desired position using asuitable holding jig. Then, the composite frame elements are coupledtogether by bonding core material 320 to the inside surfaces of thecomposite frame elements. The core material 320 can be attached to thecomposite frame elements using a suitable foaming adhesive. In addition,composite skins 316/318 are affixed to outer frame 314 and to corematerial 320, thus sandwiching the extruded composite frame elements andcore material 320 between composite skins 316/318. Composite skins316/318 may be bonded to outer frame 314 and core material 320 using anappropriate adhesive. Thereafter, this subassembly may be subjected topressure (using a press and/or a vacuum) and heat for curing, resultingin composite structural box 302.

Composite brace 304/336 is preferably formed as another compositeextrusion (e.g., one having a composition of PEKK and carbon graphitefiber layers); the same continuous compression molding process can beutilized to form this extrusion. The extruded stock is then cut to formthe opening 334 and the opposing flanges. The mounting holes in theflanges of composite brace 304/336 (the dashed lines in FIG. 22 and FIG.23 represent these holes) and the corresponding mounting holes throughstructural box 302 (see FIG. 19) may be pre-drilled. Alternatively,composite brace 304/336 may be positioned and held onto structural box302 such that the mounting holes can be drilled through the entiresubassembly in one step.

Composite brace 304/336 is then coupled to structural box 302 usingsuitably configured fasteners. For example, shoulder bolts may beinserted into the mounting holes and tightened to secure the flanges ofcomposite brace 304/336 to structural box 302. Shoulder bolts aredesirable to prevent excessive compression of structural box 302, whichmight damage core material 320 and/or outer frame 314. Alternatively,metal sleeves could be fitted through the structural box 302, allowingthe use of standard fasteners.

Rear fitting 308 may be formed from a lightweight metal such as aluminumor titanium, a high strength molded plastic, a composite, or anysuitable material or combination of materials. Rear fitting 308 ispreferably formed from a cast or milled lightweight and strong metal,e.g., titanium. As shown in FIG. 16 and FIG. 20, rear fitting 308 may beshaped to fit within the channel formed by composite brace 304/336. Rearfitting 308 is coupled to the end of composite brace 304/336 usingsuitable fasteners, such as rivets or bolts. Composite support leg 300may employ a rigid front fitting (e.g., front fitting 306) or ashock-absorbing front fitting (e.g., front fitting 344). Front fitting306 is preferably formed from a cast or milled lightweight and strongmetal such as titanium. As shown in FIG. 16 and FIG. 21, front fitting306 may be shaped to fit within the channel formed by outer frame 314(near foot end 312 of structural box 302). Pad-up area 324 providesreinforcement for the mounting of front fitting 306. Front fitting 306is coupled to structural box 302 using suitable fasteners, such asrivets, bolts, or shoulder bolts. Referring to FIG. 24 and FIG. 25,shock-absorbing front fitting 344 may also be formed from a cast ormilled lightweight and strong metal such as titanium. Moreover, frontfitting 344 is manufactured to have the characteristics andconfiguration described above. Front fitting 344 may be shaped to fitwithin the channel formed by outer frame 314 (at the lower aft sectionof structural box, near foot end 312). Pad-up area 324 providesreinforcement for the mounting of front fitting 344. Front fitting 344is coupled to structural box 302 using suitable fasteners, such asrivets, bolts, or shoulder bolts.

For one exemplary triple seat configuration, two composite support legs300 can then be readied for attachment to composite seat pan 200.Referring to FIG. 15 and FIG. 19, structural box 302 is drilled to matchthe mounting hole pattern of spreader bars 208. For this embodiment,these mounting holes are drilled around the flange of outer frame 314.These mounting holes may be pre-drilled in structural box 302 and/orspreader bars 208. Alternatively, composite support leg 300 may bepositioned and held in place relative to one or more spreader bars 208(as shown in FIG. 4 and FIG. 5) such that the mounting holes can bedrilled through support leg 300 and spreader bars 208 in one step.Regardless of the specific drilling procedure, support legs 300 arecoupled to seat pan 200 via spreader bars 208. In practice, each supportleg 300 is attached to one or more spreader bars 208 using suitablefasteners, such as rivets, bolts, or shoulder bolts. The resultingsubassembly can then be readied for attachment of the composite seatback structure (described below) and/or other seat components.

Composite Seat Back Structure

Each composite seat back structure 400 employs a composite constructionthat is lightweight and producible in a cost-efficient manner. Forexample, each composite seat back structure 400 can be manufacturedusing molded composites, resulting in a weight of less than 3.0 pounds.FIG. 26 depicts one embodiment of a composite seat back structure 400 a,and FIG. 30 depicts another embodiment of a composite seat backstructure 400 b.

Referring to FIGS. 26-29, composite seat back structure 400 a generallyincludes a support frame 402, a torque box 404 coupled to support frame402, and an actuator rib 406 coupled to torque box 404. FIG. 26 is aperspective view of composite seat back structure 400 a, FIG. 27 is aperspective view of an embodiment of torque box 404, FIG. 28 is aperspective cross sectional view of composite seat back structure 400 ashown in FIG. 26 cut through the major section of torque box 404, andFIG. 29 is a perspective view of an embodiment of actuator rib 406.

Support frame 402 may be formed from a composite construction, alightweight metal such as aluminum or titanium, a high strength moldedplastic, or any suitable material or combination of materials. In thisembodiment, support frame 402 may be realized as a one-piece componenthaving an upper end 408 and a lower end 410. Upper end 408 correspondsto the upper back or headrest area of the passenger seat, while lowerend 410 corresponds to the lumbar or hip area of the seat. Support frame402 generally includes an arch segment 412 at upper end 408, opposingside segments 414 extending from arch segment 412, and curved legs 416extending from side segments 414. Referring to FIG. 6, support frame 402may have a gradually contoured profile that is designed for comfortablesupport of the passenger. When deployed, a textile diaphragm mesh or webelement (not shown) may be installed on support frame 402 to form theseat back cushion and provide occupant back support.

In one embodiment, support frame 402 is a tube (for example, a square orrectangular tube) having a non-uniform gauge. For example, the gauge ofthe tube at curved legs 416 is preferably thicker than the gauge of thetube at arch segment 412 and at side segments 414. This additionalthickness provides increased strength at curved legs 416, where highertorque is experienced. Moreover, the gauge of the tube at side segments414 may be thicker than the gauge of the tube at arch segment 412. Thisvariable gauge of support frame 402 may be desirable to reduce theweight of composite seat back structure 400 a without compromising thestructural integrity and performance of support frame 402. For example,the tube may have a nominal wall thickness of about 0.05 inch, where thewall thickness at arch segment is about 0.03 inch and the wall thicknessat curved legs 416 is about 0.08 inch.

In certain embodiments, support frame 402 is formed as a compositeconstruction using a suitable molding technique. In one embodiment,support frame 402 is formed from a thermoplastic resin (such as PEKK,for the reasons mentioned above) and at least one layer of carbongraphite fiber material. It should be appreciated that other compositematerials, resins, and fibers may be used in an embodiment of supportframe 402.

Torque box 404 may be formed from a composite construction, alightweight metal such as aluminum or titanium, a high strength moldedplastic, or any suitable material or combination of materials. Torquebox 404 may be coupled to, or integrated into, lower end 410 of supportframe 402. Torque box 404 is suitably configured to secure curved legs416 relative to each other and to structurally reinforce support frame402. In this regard, torque box 404 is configured to resist fore-aftbending of support frame (the bending mode that would otherwise becaused when the passenger leans back against the seat back). Moreover,torque box 404 is configured to transfer loads from composite seat backstructure 400 a to seat pan 200 via rear flange 222 of aft cross beam204 as described above.

For this example, torque box 404 includes an outer frame 418, an upperskin 420, a lower skin 422, and core material 424 located within outerframe 418 and between upper skin 420 and lower skin 422. Core material424 stabilizes upper skin 420 and lower skin 422 such that skins 420/422do not buckle or deform. Outer frame 418 may be produced from extrudedcomposite elements formed from a thermoplastic resin (e.g., PEKK) and atleast one layer of carbon graphite fiber material, as described above inthe context of composite cross beams 202/204 for seat pan 200. Moreover,upper skin 420 and lower skin 422 may each be produced from athermoplastic resin (e.g., PEKK) and at least one layer of fibermaterial (e.g., aramid fiber material and/or carbon graphite fibermaterial). Core material 424 may utilize any suitable material, such asthat described above for core material 320 of composite support leg 300.

As best shown in FIG. 27 and FIG. 28, the two side sections of outerframe 418 may serve as mounting channels for curved legs 416 ofcomposite support frame 402. Curved legs 416 can be attached to outerframe 418 using a suitable bonding adhesive, welding techniques, and/orusing fasteners such as rivets or bolts. Alternatively, it may bepossible to form an integrated component that includes support frame 402and torque box 404 (or sections thereof).

The illustrated embodiment also includes actuator rib 406 coupled tocomposite torque box 404. In practice, actuator rib 406 can be formed ofa lightweight metal such as aluminum or titanium. Actuator rib 406 maybe cast from such metal for ease of manufacturing. In one embodiment,actuator rib 406 can be attached to a curved leg 416 using a suitablebonding adhesive and/or using fasteners such as rivets or bolts.

Referring to FIG. 29, actuator rib 406 may have a mounting channel orshoulder 425 formed therein. Shoulder 425 is configured to generallyfollow the contour of composite torque box 404 at the location shown inFIG. 26. Actuator rib 406 is shaped and configured as a moment arm foran actuator 426 (see FIG. 7 and FIG. 24), where actuator 426 regulatesthe pivoting rate of composite seat back structure 400 a relative toseat pan 200. In this regard, actuator rib 406 includes an extension 428having a mounting hole 430 formed therein. As shown in FIG. 7, one endof actuator 426 is coupled to mounting hole 430. The other end ofactuator 426 may be coupled to an appropriate feature or element ofcomposite support leg 300 and/or to an appropriate feature or element ofa spreader bar 208.

In this example, composite seat back structure 400 a need not use morethan one actuator rib 406. Rather, seat back structure 400 a is suitablyconfigured such that a single actuator rib 406 can serve as a lever foractuator 426. Each seat back utilizes only one actuator 426, andactuator rib 406 increases the moment arm to enable easier actuation ofseat back structure 400 a relative to seat pan 200. When released,actuator 426 allows seat back structure 400 a to pivot relative to seatpan 200; when engaged, actuator 426 maintains the position of seat backstructure 400 a relative to seat pan 200. Thus, actuator 426 andactuator rib 406 provide structural support to prevent seat backstructure 400 a from inadvertently moving.

As described above in the context of seat pan 200, composite seat backstructure 400 a is preferably configured to be attached to composite aftcross beam 204 of seat pan 200 in a manner than allows seat backstructure 400 a to recline relative to aft cross beam 204. Inparticular, the lower surface of rear flange 222 of aft cross beam 204may be coupled to composite torque box 404 such that rear flange 222 canserve as a flexible and resilient hinge for seat back structure 400 a(see FIG. 8 and FIG. 28). In addition, the return spring contained intraditional actuators could be eliminated by taking advantage of thenatural resiliency of the composite hinge. In other words, the hingeformed by joining the aft cross beam 204 to the composite torque box 404acquires sufficient energy when deflected to return the seat back to itsun-deflected position once released. Here, rear flange 222 can beattached to outer frame 418 of torque box 404 using a suitable bondingadhesive and/or using fasteners such as rivets or bolts. In thisembodiment, rear flange 222 represents the only structural couplingpoint between seat back structure 400 a and seat pan 200. Notably, thisconfiguration eliminates the need for a distinct hinge assembly or anyrotating machinery at the junction of seat back structure 400 a and seatpan 200, resulting in a simpler design and less overall weight for theaircraft seat. Importantly, this configuration eliminates the proceduresand costs normally associated with the maintenance of seat hingeassemblies, which traditionally represents one of the higher maintenancecosts of aircraft seats.

For ease of production, composite seat back structure 400 may instead beconfigured such that a separate torque box need not be utilized. Such anembodiment of composite seat back structure 400 b is shown in FIG. 30and FIG. 31. Composite seat back structure 400 b generally includes afirst half-shell 432 and a second half-shell 434 that are coupledtogether into a single component. The dashed line in FIG. 30 representsa seam or joint between half-shells 432/434.

Each half-shell 432/434 may be formed from a composite construction, alightweight metal such as aluminum or titanium, a high strength moldedplastic, or any suitable material or combination of materials. For thisexample, each of the half-shells 432/434 is realized as a composite thatis formed using a suitable molding technique. In one embodiment, eachhalf-shell 432/434 is formed from a thermoplastic resin (such as PEKK,for the reasons mentioned above) and at least one layer of carbongraphite fiber material. It should be appreciated that other compositematerials, resins, and fibers may be used in an embodiment of compositeseat back structure 400 b.

Notably, FIG. 30 may also generally represent the profile view ofcomposite seat back structure 400 a (see FIG. 26). In this regard,composite half-shell 432 corresponds to the forward-facing portion ofcomposite seat back structure 400 b, and composite half-shell 434corresponds to the rear-facing portion of seat back structure 400 b. Inthis embodiment, half-shell 432 includes a support frame segment 436having an upper end and a lower end, and an integral skin element 438located at the lower end of support frame segment 436. Likewise,half-shell 434 includes a support frame segment 440 having an upper endand a lower end, and an integral skin element 442 located at the lowerend of support frame segment 440. The dashed lines in FIG. 29 representskin elements 438/442.

Referring to FIG. 31, seat back structure 400 b may also include corematerial 444 located between skin elements 438/442. As mentioned above,half-shells 432/434 may be coupled or formed together into a singlecomponent such that skin elements 438/442 and core material 444 form anintegral torque box for seat back structure 400 b. In contrast to thatdepicted in FIG. 28, core material 444 fully extends to the outerperimeter of the torque box, where the outer perimeter is defined byskin elements 438/442 and the two side walls of the lower end ofhalf-shells 432/434. Core material 444 may be formed as a distinct piecethat is subsequently bonded between composite half-shells 432/434 duringassembly. Alternatively, core material 444 may be integrally formed intoone or both half-shells 432/434 during the molding of half-shells432/434.

After it is produced, composite seat back structure 400 b may have thecharacteristics, features, and functionality described above in thecontext of composite seat back structure 400 a. For the sake of brevity,such common aspects will not be redundantly described here in thecontext of seat back structure 400 b.

While at least one example embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexample embodiment or embodiments described herein are not intended tolimit the scope, applicability, or configuration of the invention in anyway. Rather, the foregoing detailed description will provide thoseskilled in the art with a convenient road map for implementing thedescribed embodiment or embodiments. It should be understood thatvarious changes can be made in the function and arrangement of elementswithout departing from the scope of the invention, where the scope ofthe invention is defined by the claims, which includes known equivalentsand foreseeable equivalents at the time of filing this patentapplication.

1. A composite seat pan for a lightweight aircraft passenger seat, thecomposite seat pan comprising: a composite fore cross beam; a compositeaft cross beam; and a composite skin having an upper surface and anopposite lower surface coupled to the composite fore cross beam and tothe composite aft cross beam, the composite skin being configured as astructural element of the composite seat pan that resists fore-aftbending of the composite fore cross beam and the composite aft crossbeam.
 2. A composite seat pan according to claim 1, wherein each of thecomposite fore cross beam and the composite aft cross beam is anextruded composite beam.
 3. A composite seat pan according to claim 2,wherein each of the composite fore cross beam and the composite aftcross beam is a continuous compression molded composite beam.
 4. Acomposite seat pan according to claim 2, wherein each of the compositefore cross beam and the composite aft cross beam comprises athermoplastic resin and at least one layer of carbon fiber material. 5.A composite seat pan according to claim 4, wherein thethermoplastic-resin comprises polyetherketoneketone (PEKK).
 6. Acomposite seat pan according to claim 1, further comprising a pluralityof spreader bars, each comprising: a fore flange coupled to thecomposite fore cross beam; an aft flange coupled to the composite aftcross beam; and an upper flange coupled to the lower surface of thecomposite skin.
 7. A composite seat pan according to claim 1, whereinthe composite skin comprises a thermoplastic resin and at least onelayer of aramid fiber material.
 8. A composite seat pan according toclaim 7, wherein: the aramid fiber material comprises KEVLAR material;and the thermoplastic resin comprises polyetherketoneketone (PEKK).
 9. Acomposite seat pan according to claim 7, wherein the composite skinfurther comprises reinforcing areas formed with at least one layer ofcarbon fiber material.
 10. A composite seat pan according to claim 1,wherein each of the composite fore cross beam and the composite aftcross beam has an asymmetric longitudinal cross section that provides adirectional load-bearing characteristic.
 11. A composite seat panaccording to claim 1, wherein the composite aft cross beam includes arear flange configured for coupling to a seat back of the lightweightaircraft passenger seat, the rear flange being flexible and resilient tofacilitate formation of a hinge between the seat back and the compositeseat pan.
 12. A composite seat pan according to claim 11, wherein therear flange of the composite aft cross beam has an upper surface coupledto the lower surface of the composite skin, and a lower surfaceconfigured for coupling to the seat back.
 13. A method of manufacturinga composite seat pan for a lightweight aircraft passenger seat, themethod comprising: forming a fore cross beam from a first compositeextrusion using a continuous compression molding process; forming an aftcross beam from a second composite extrusion using the continuouscompression molding process; structurally joining the fore cross beam tothe aft cross beam with a plurality of spreader bars; and structurallycoupling a composite skin to the fore cross beam, the aft cross beam,and the spreader bars.
 14. A method according to claim 13, wherein:forming the fore cross beam comprises forming the first compositeextrusion from a first plurality of plies; forming the aft cross beamcomprises forming the second composite extrusion from a second pluralityof plies; and each of the plies comprises a thermoplastic resin and atleast one layer of carbon graphite fiber material.
 15. A methodaccording to claim 14, wherein the thermoplastic resin comprisespolyetherketoneketone (PEKK).
 16. A method according to claim 13,further comprising forming the composite skin from a thermoplastic resinand at least one layer of aramid fiber material.
 17. A method accordingto claim 16, wherein forming the composite skin comprises reinforcingthe composite skin in attachment areas corresponding tocross-beam-to-skin junctions and spreader-bar-to-skin junctions.
 18. Amethod according to claim 17, wherein reinforcing the composite skincomprises adding at least one layer of carbon graphite fiber material inthe attachment areas.
 19. A method according to claim 13, wherein:forming the fore cross beam comprises forming, in a first layup, thefirst composite extrusion from material having directional fibers, whereat least thirty percent of the fibers in the first composite extrusionare oriented within the range of ±30 degrees relative to the majorlongitudinal axis of the first composite extrusion; and forming the aftcross beam comprises forming, in a second layup, the second compositeextrusion from material having directional fibers, where at least thirtypercent of the fibers in the second composite extrusion are orientedwithin the range of ±30 degrees relative to the major longitudinal axisof the second composite extrusion.
 20. A method according to claim 19,wherein: in the first layup, more than fifty percent of the fibers inthe first composite extrusion are oriented at approximately ±5 degreesrelative to the major longitudinal axis of the first compositeextrusion, and less than fifty percent of the fibers in the firstcomposite extrusion are oriented at approximately ±65 degrees relativeto the major longitudinal axis of the first composite extrusion; and inthe second layup, more than fifty percent of the fibers in the secondcomposite extrusion are oriented at approximately +5 degrees relative tothe major longitudinal axis of the second composite extrusion, and lessthan fifty percent of the fibers in the second composite extrusion areoriented at approximately ±65 degrees relative to the major longitudinalaxis of the second composite extrusion.
 21. A method according to claim20, wherein: in the first layup, approximately eighty percent of thefibers in the first composite extrusion are oriented at approximately ±5degrees relative to the major longitudinal axis of the first compositeextrusion, and approximately twenty percent of the fibers in the firstcomposite extrusion are oriented at approximately ±65 degrees relativeto the major longitudinal axis of the first composite extrusion; and inthe second layup, approximately eighty percent of the fibers in thesecond composite extrusion are oriented at approximately ±5 degreesrelative to the major longitudinal axis of the second compositeextrusion, and approximately twenty percent of the fibers in the secondcomposite extrusion are oriented at approximately ±65 degrees relativeto the major longitudinal axis of the second composite extrusion. 22.composite seat plan assembly for a lightweight aircraft passenger seat,the composite seat plan assembly comprising: a composite fore crossbeam; a composite aft cross beam having a rear flange configured forcoupling to a seat back of the lightweight aircraft passenger seat, therear flange being flexible and resilient to facilitate pivoting of thedeat back relative to the composite aft cross beam; and a composite skinhaving an upper surface and an opposite lower surface coupled to thecomposite fore cross beam and to the composite aft cross beam.
 23. Acomposite seat pan assembly according to claim 22, wherein the rearflange of the composite aft cross beam has an upper surface coupled tothe lower surface of the composite skin, and a lower surface configuredfor coupling to the seat back.
 24. A composite seat pan assemblyaccording to claim 22, further comprising a seat back component coupledto the rear flange of the composite aft cross beam, wherein the rearflange of the composite aft cross beam serves as a hinge between thecomposite skin and the seat back.
 25. A composite seat pan assemblyaccording to claim 22, wherein: the composite fore cross beam has anon-uniform cross section, relative to its major longitudinal axis, thatreinforces the composite fore cross beam at a mounting location for asupport leg of the lightweight aircraft passenger seat; and thecomposite aft cross beam has a non-uniform cross section, relative toits major longitudinal axis, that reinforces the composite aft crossbeam at a mounting location for a support leg of the lightweightaircraft passenger seat.
 26. A composite seat pan assembly according toclaim 22, wherein: the composite skin includes a reinforcing strip at anattachment area corresponding to a cross-beam-to-skin junction; and thereinforcing strip has a non-uniform cross section, relative to its majorlongitudinal axis, that reinforces the composite skin at a mountinglocation for a support leg of the lightweight aircraft passenger seat.27. A composite seat pan assembly according to claim 22, furthercomprising seat belt anchors coupled to the composite aft cross beam.28. A composite seat pan assembly according to claim 27, furthercomprising a plurality of spreader bars, each comprising: a fore flangecoupled to the composite fore cross beam; an aft flange coupled to thecomposite aft cross beam; and a rib between the fore flange and the aftflange; wherein the seat belt anchors are aligned with the ribs of thespreader bars.